Helmet shell

ABSTRACT

A helmet includes a helmet shell having an outer surface, an inner surface, and a plurality of slit openings. Each slit opening extends along a portion of the helmet shell. The slit openings include a pair of top slit openings that each extend longitudinally along a top portion of the helmet shell, where each top slit opening has a first length. The pair of top slit opening are spaced apart and define a flexible helmet portion spaced between the pair of top slit openings. The flexible helmet portion extends along the first length from a first end of the flexible helmet portion to a second end of the flexible helmet portion opposite to the first end, and the flexible helmet portion has a stiffness that varies along the first length from the first end to the second end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 63/242,895, filed on Sep. 10, 2021, thedisclosure of which is incorporated by reference herein in its entiretyfor all purposes.

TECHNICAL FIELD

This disclosure relates to a helmet shell, for example, for helmetsadapted for contact sports.

BACKGROUND

Many modern organized sports employ helmets that are designed to providethe players with significant head protection, with the desire to provideadequate protection from traumatic brain injury (TBI). Since safety is aprimary concern, helmets have continually evolved in an attempt toreduce the risk and rate of concussions and/or other repetitive braininjuries, which can potentially end a player's career early and lead tolong-term brain damage. This is especially true in American football,where the essential character of the athletic contest involves repeatedplayer contacts, impacts, and tackling.

However, most helmet designs (e.g., for football or other sports oractivities) fail to protect or provide inadequate protection againstsome of the most dangerous impacts within a game.

SUMMARY

This disclosure describes helmets, including helmet shells with slitopenings in an outer surface of the helmets.

In some aspects of the disclosure, a helmet includes a helmet shellhaving an outer surface, an inner surface, and a plurality of slitopenings. Each slit opening extends along a portion of the helmet shell,and the slit openings include a pair of top slit openings that eachextend longitudinally along a top portion of the helmet shell. Each topslit opening of the pair of top slit openings has a first length. Thepair of top slit opening are spaced apart and define a flexible helmetportion spaced between the pair of top slit openings. The flexiblehelmet portion extends along the first length from a first end of theflexible helmet portion to a second end of the flexible helmet portionopposite to the first end, and the flexible helmet portion has astiffness that varies along the first length from the first end to thesecond end.

This, and other aspects, can include one or more of the followingfeatures. The stiffness of the flexible helmet portion can include afirst stiffness at the first end and at the second end of the flexiblehelmet portion, a second stiffness at a middle portion of the flexiblehelmet portion between the first end and the second end, and a thirdstiffness at an intermediate portion of the flexible helmet portionbetween the first end and the middle portion. The first stiffness can begreater than the second stiffness, and the third stiffness can begreater than the second stiffness and less than the first stiffness. Thehelmet can include a plurality channels recessed in the outer surface ofthe helmet shell, the plurality of channels including a pair of topchannels along the top portion of the helmet shell, and the pair of topslit openings can reside within the pair of top channels. The pair oftop slit openings can be arranged substantially parallel to each otheralong the top portion of the helmet shell. The pair of top slit openingscan be symmetrical with each other across a lateral centerline of thehelmet shell. The pair of top slit openings can be linear. Each of thetop slit openings can include a laterally outward curve. The top slitopening of each top channel of the pair of top channels can extend alonga majority of a length of the pair of top channels. The helmet shell caninclude a central recession in the outer surface of the helmet shell ina crown region between the pair of top slit openings. The plurality ofslit openings can further include a pair of left side slit openingsextending along a left side of the helmet shell toward a rear of thehelmet shell, and a pair of right side slit openings extending along aright side of the helmet shell toward the rear of the helmet shell. Eachleft side slit opening of the pair of left side slit openings can have asecond length, the pair of left side slit opening can be spaced apartand can define a second flexible helmet portion spaced between the pairof left side slit openings, and the second flexible helmet portion canextend along the second length from a first end of the second flexiblehelmet portion to a second end of the second flexible helmet portionopposite to the first end, and the second flexible helmet portion canhave a stiffness that varies along the second length from the first endto the second end of the second flexible helmet portion. The stiffnessof the second flexible helmet portion can include a first stiffness atthe first end and at the second end of the second flexible helmetportion, a second stiffness at a middle portion of the second flexiblehelmet portion between the first end and the second end, and a thirdstiffness at an intermediate portion of the second flexible helmetportion between the first end and the middle portion. The firststiffness can be greater than the second stiffness, and the thirdstiffness can be greater than the second stiffness and less than thefirst stiffness. The helmet can include a plurality channels recessed inthe outer surface of the helmet shell, the plurality of channels caninclude a pair of left side channels along the left side of the helmetshell and a pair of right side channels along the right side of thehelmet shell, the pair of left side slit openings can reside within thepair of left side channels, and the pair of right side slit openings canreside within the pair of right side channels.

In certain aspects, a helmet shell includes a shell body, an outersurface of the shell body, an inner surface of the shell body, and aplurality of slit openings. Each slit opening extends along a portion ofthe helmet shell, and the plurality of slit openings include a pair ofleft side slit openings extending along a left side of the shell bodytoward a rear of the shell body, where each left side slit opening ofthe pair of left side slit openings includes a first length, and a pairof right side slit openings extending along a right side of the shellbody toward a rear of the shell body, where each right side slit openingof the pair of right side slit openings includes a second length. Thepair of left side slit openings are spaced apart and define a leftflexible helmet portion between the pair of left side slit openings, theleft flexible helmet portion extending along the first length from afirst end of the left flexible helmet portion to a second end of theleft flexible helmet portion opposite to the first end, and the leftflexible helmet portion includes a stiffness that varies along the firstlength from the first end to the second end. The pair of right side slitopenings are spaced apart and define a right flexible helmet portionbetween the pair of right side slit openings, the right flexible helmetportion extending along the second length from a third end of the rightflexible helmet portion to a fourth end of the right flexible helmetportion opposite to the third end, and the right flexible helmet portionincludes a stiffness that varies along the second length from the thirdend to the fourth end.

This, and other aspects, can include one or more of the followingfeatures. The stiffness of the left flexible helmet portion includes afirst stiffness at the first end and at the second end of the leftflexible helmet portion, a second stiffness at a middle portion of theleft flexible helmet portion between the first end and the second end,and a third stiffness at an intermediate portion of the left flexiblehelmet portion between the first end and the middle portion. Thestiffness of the right flexible helmet portion includes the firststiffness at the third end and at the fourth end of the right flexiblehelmet portion, the second stiffness at a second middle portion of theright flexible helmet portion between the third end and the fourth end,and the third stiffness at a second intermediate portion of the rightflexible helmet portion between the third end and the second middleportion. The first stiffness is greater than the second stiffness, andthe third stiffness is greater than the second stiffness and less thanthe first stiffness. The helmet shell can include a plurality channelsrecessed in the outer surface of the helmet shell, the plurality ofchannels can include a pair of left side channels along the left side ofthe helmet shell and a pair of right side channels along the right sideof the helmet shell, the pair of left side slit openings reside withinthe pair of left side channels, and the pair of right side slit openingsreside within the pair of right side channels. The pair of left sideslit openings and the pair of right side slit openings can be linear.

Some aspects of the disclosure encompass a helmet shell including ashell body, an outer surface and an inner surface of the shell body, anda plurality of slit openings extending along a portion of the helmetshell. The plurality of slit openings include a pair of rear slitopenings at a rear of the helmet shell, the pair of rear slit openingspartially surrounding a rear zone at the rear of the helmet shell andinclude a first length.

This, and other aspects, can include one or more of the followingfeatures. The pair of rear slit openings can be spaced apart and candefine a rear flexible helmet portion between the pair of rear slitopenings, the rear flexible helmet portion can extend along the firstlength from a first end of the rear flexible helmet portion to a secondend of the rear flexible helmet portion opposite to the first end, andthe rear flexible helmet portion can include a stiffness that variesalong the first length from the first end to the second end. Thestiffness of the rear flexible helmet portion can include a firststiffness at the first end and at the second end of the rear flexiblehelmet portion, a second stiffness at a middle portion of the rearflexible helmet portion between the first end and the second end, and athird stiffness at an intermediate portion of the rear flexible helmetportion between the first end and the middle portion. The firststiffness can be greater than the second stiffness, and the thirdstiffness can be greater than the second stiffness and less than thefirst stiffness. The pair of rear slit openings can be straight. Thepair of rear slit openings can be symmetrical across a lateralcenterline of the helmet shell.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are a front perspective view and a rear perspective view,respectively, of an example helmet shell.

FIG. 3 is a rear view of the example helmet shell of FIG. 1 .

FIG. 4 is a rear perspective view of the example helmet shell of FIG. 1.

FIG. 5 is a side view of the example helmet shell of FIG. 1 .

FIG. 6 is a top view of the example helmet shell of FIG. 1 .

FIGS. 7 and 8 are a front view and a front perspective view,respectively, of a second example helmet shell.

FIG. 9 is a rear view of the second example helmet shell of FIG. 7 .

FIG. 10 is a rear perspective view of the second example helmet shell ofFIG. 7 .

FIG. 11 is a side view of the second example helmet shell of FIG. 7 .

FIG. 12 is a top view the second example helmet shell of FIG. 7 .

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

This disclosure describes a helmet shell with one or more slit openingsthrough an outer surface of the helmet shell that provide areas ofvarying stiffness and flexibility of the helmet shell. The slit openingscan provide increased stiffness in certain areas of the helmet and/orcan provide flexible zones (e.g., zones between slit openings). Theflexible zones are defined by varying stiffness that can transition fromhigh-to-low-to-high stiffness, and are aimed at mitigating ordistributing energy and/or force of impacts to the helmet during use.For example, the varying stiffness in the outer surface of the helmetcan transition from a zone of high stiffness, low stiffness, andintermediate stiffness between the high stiffness and low stiffness. Insome instances, the slit openings reside in recessed channels in theouter surface of the helmet shell, and the channels can define variouszones of the helmet. The slit openings, and in some instances, thechannels and the slit openings, can provide increased stiffness in areasthat are prone to higher volume of impacts, such as sides and rear zonesof the helmet relative to a top zone, or crown, of the helmet thatgenerally encounters fewer impacts.

The slit openings can be through-openings that extend from an outersurface to an inner surface of the helmet shell, and the slit openingsare continuous openings that span a certain length along the helmetshell. An example slit opening includes a length that is considerablylarger than its width, such as a length that is one or more inches longand a width that is less than a half inch. The dimensions of the slitopenings can vary, but generally include a longitudinal length that isat least three times its width. The openings can also act to ventilatethe outer shell. In some implementations, the slit openings include apair of parallel slit openings in one or more of areas of the helmet,e.g., a pair of parallel slit openings spanning a portion of the top ofthe helmet (e.g., openings running from a front of the helmet and alonga top of the helmet toward the back of the helmet), one or more pairs ofparallel side slit openings spanning a portion of one or both sides ofthe helmet (e.g., openings running from the front of the helmet alongsides of the helmet toward the back of the helmet), and/or one or moreparallel rear slit openings spanning a portion of the rear of the helmet(e.g., a openings extending through the rear/back of the helmet, such asfrom one side of the helmet to the other). The helmet can includedifferent or additional slit openings through helmet shell.Additionally, in some implementations, one or more pairs of slit openingneed not be parallel to each other.

FIGS. 1 and 2 are a front view and a front perspective view,respectively, of an example helmet shell 100 with multiple slit openingsthrough the helmet shell 100. The slit openings are disposed along anouter surface 104 of the helmet shell 100. FIGS. 3, 4, 5, and 6 are arear view, rear perspective view, side view, and top view, respectively,of the example helmet shell 100 with the multiple slit openings. Theslit openings are disposed over various zones of the example helmetshell 100, such as on the top, sides, and rear of the helmet shell 100.The slit openings, which are described in greater detail below, createflexible portions of the helmet shell 100 between the slit openings, andthese flexible portions of the helmet shell 100 have varying stiffness.For example, the stiffness of the flexible zones can vary at thelongitudinal ends of the flexible portions, at a center of the flexibleportions, and/or at intermediate areas of the flexible portions betweenthe center and the ends.

In some instances, the flexible portions of the helmet shell 100 have aprogressive stiffness, in that the stiffness of the flexible portionprogressively decreases from a first longitudinal end to a middle of theflexible portion, then progressively increases from the middle to thesecond, opposite longitudinal end of the flexible portion. The flexibleportions are most flexible at the areas of lowest stiffness, and leastflexible at the areas of highest stiffness. Moreover, provision offlexible portions in the helmet via use of the spaced apart slitopenings enables achieving varying stiffness at different zones acrossthe helmet and by extension, varying the impact response at thesedifferent zones. For example, a conventional spherical helmet generallyhas the same stiffness throughout the helmet such that an impact to thehelmet has the same impact response, regardless of where the impact wasmade on the spherical helmet. In contrast, a helmet formed with parallelor spaced apart slit openings in some portions of the helmet but notothers allows the helmet to have varying impact responses, e.g., certainportions of the helmet can be stiffer (e.g., at a front portion of thehelmet where the faceguard is attached to the helmet) and offer aparticular impact response compared to the flexible zones (defined bythe space between the slit openings) that are relatively more flexibleand offer a different impact response. Thus, the use of slit openingsand the defined flexible zones therebetween allows customizing andadjusting the impact response for different portions of the helmet. Indoing so, the helmet can be further outfitted with impact absorbing padsor other materials that are customized for the certain areas of thehelmet corresponding to the flexible zone(s) as well as for otherportions of the helmet having different stiffness (e.g., higherstiffness).

In the example helmet shell 100 of FIGS. 1-6 , multiple pairs of slitopenings are shown disposed within multiple channels 102. The multiplechannels 102 form an interconnected grid of channels in the outersurface 104 of the helmet shell 100, and all or a portion of the slitopenings are disposed within the multiple channels 102. However, theexample helmet shell 100 can include the multiple pairs of slit openingswithout the multiple channels 102 in the helmet shell 100. For example,the multiple slit openings can be formed as cuts in the shell body ofthe example helmet shell 100 that extend from the outer surface 106 tothe inner surface 104 (separate from any channels, if any are present inthe helmet shell), or as cuts in the recessed channels 102 of theexample helmet shell 100, or a combination of these. While the examplehelmet shell 100 depicts the slit openings as disposed within themultiple recessed channels 102, the slit openings do not need to residein the channels 102, and the example helmet shell 100 does not need toinclude these multiple channels 102 either. For example, the examplehelmet shell 100 can exclude the channels 102 such that the slitopenings are formed in the body of the helmet shell 100.

The slit openings of the example helmet shell 100 includes a pair of topslit openings 120 along a top or crown region of the helmet shell 100, apair of left side slit openings 134 extending along a left side of thehelmet shell 100 toward the rear of the helmet shell 100, a pair ofright side slit openings extending along a right side of the helmetshell 100 toward the rear of the helmet shell 100 (e.g., mirroring theleft side openings 134 on the opposite side of the helmet shell 100),and a pair of rear slit openings 146 extending along the rear of thehelmet in a generally vertical direction and toward a bottom edge of thehelmet shell 100 at the rear of the helmet shell 100. Other embodimentsof helmet shells may include a different arrangement of slit openings,additional openings, or fewer openings in the outer surface 104 thanthose slit openings depicted in the example helmet shell 100 of FIGS.1-6 .

In some instances, the multiple slit openings define the various zonesof the helmet shell 100, for example, by bordering (partially orcompletely) these various zones. The slit openings are described ingreater detail below. Some of the zones, such as zones on the side andrear of the helmet shell 100, are prone to a higher volume of impactduring sporting activity during activities like football gameplay. Theslit openings create zones of varying stiffness, such that an impactforce against a zone can be dispersed along the flexible portionsbetween the slit openings, and the flexile portions can dent and flexwhen impacted by an impact force.

The example helmet shell 100 can be used in a helmet, which may alsoinclude liners, padding layers, facemasks (e.g., to protect a wearer'sface), and/or other features in combination with the example helmetshell 100. The liners and/or padding layers, in combination with thehelmet shell 100, can help further absorb, dampen, disperse, and/ordeflect forces from impacts against the helmet. The helmet, includingthe example helmet shell 100, encloses the top, back, and sides of awearer's head, and a front of the helmet is desirably open to provide anunobstructed line of sight for the wearer of the helmet. While not shownin FIGS. 1-6 , the example helmet shell 100 can include perforations,openings, snaps, or other connection points, for example, to connect oneor more helmet components to the example helmet shell 100, such as chinstraps, facemasks, plate extensions (e.g., jaw plates), a combination ofthese, or other components. The helmet shell of the present disclosureis described for use in helmets for American football, though the helmetshells can be applicable to other sports, such as baseball, ice hockey,lacrosse, motorsports, cycling, snow sports, or other sports oractivities that utilize helmets for head protection and/or impactmitigation.

The helmet shell 100 can be manufactured from a rigid or substantiallyrigid material, such as polyethylene, nylon, polycarbonate materials,acrylonitrile butadiene styrene (ABS), polyester resin with fiberglass,thermosetting plastics, and/or other rigid thermoplastic materials.Alternatively, the helmet shell 100 can be manufactured from arelatively deformable material, such as polyurethane and/or high-densitypolyethylene, where such material allows some flexibility and/or localdeformation of the helmet shell 100 (and/or an impact mitigation layerattached to an inner surface of the helmet shell 100) upon impact, butprovide sufficient rigidity to prevent the breakage or damage to theexample helmet shell 100. The helmet shell 100 can be formed of acontinuous, single shell, or a multi-piece assembly (e.g., a two-pieceshell assembly of a front shell and a back shell) that conforms andsurrounds the head of the wearer.

The example helmet shell 100 of FIGS. 1-6 is shown as a single shellstructure. However, in some implementations, the example helmet shell100 can include more than one shell in a stacked configuration, such asan outer shell and an inner shell. For example, the outer shell cangenerally surround the inner shell, and the inner shell can be acontinuous, single shell or a multi-piece shell assembly (e.g., atwo-piece shell assembly of a front shell and a back shell) thatconforms to and surrounds the head of the wearer. The at least one innershell can be made of a rigid material, and can have greater rigiditythan the rigidity of the outer shell. In some examples, the inner shellis 5 to 100 times stiffer, or more rigid, than the outer shell. Therigid material may include polycarbonate (PC). Alternatively, the innershell can include a different material, such as a substantially rigidmaterial (e.g., polyethylene, nylon, polycarbonate materials,acrylonitrile butadiene styrene (ABS), polyester resin with fiberglass,thermosetting plastics, and/or other rigid thermoplastic materials; asdescribed above). The substantially rigid material may be stiff or rigidenough to withstand breakage or cracking, but flexible enough to deformslightly and distribute incident forces after an impact. The at leastone inner shell may include a thermoplastic material. Thermoplasticmaterials may comprise polyurethane, polycarbonate, polypropylene,polyether block amide, and/or any combinations thereof. Alternatively,the inner shell may include a deformable material, such as polyurethaneand/or high-density polyethylene, where such material allows someflexibility and/or local deformation upon impact, but provide enoughrigidity to prevent the breakage or damage to the helmet.

The example helmet shell 100 of FIGS. 1-6 can include additionalfeatures not shown. For example, the helmet shell 100 of FIGS. 1-6includes a shell body that the slit openings are formed through, andthat the multiple channels 102 are recessed into. However, the examplehelmet shell 100 can include additional features or structures coupledto or integrally formed with the shell body. The slit openings and/orchannels 102 of the example helmet shell 100 can take different formsbased on the zone that the slit openings reside in or are adjacent to.For example, some of the channels 102 may include slit openings, such asthrough openings extending from the outer surface 104 (e.g., exteriorsurface) to the inner surface 106 (e.g., interior surface) of the helmetshell 100, and/or other channels 102 may exclude a through opening. Thethrough openings may also be referred to herein as vent openings, holes,or relief vents. In certain instances, the channels 102 include arecession in the outer surface 104 of the helmet shell 100, but therecession does not extend entirely through a thickness of the helmetshell 100 to the inner surface 106 like the through openings do.Instead, the recession may extend to an intermediate dimension betweenthe outer surface 104 and the inner surface 106. In someimplementations, the channels 102 are recessed from the outer surface104 of the helmet shell 100 a depth of up to 3 millimeters. In someexamples, some or all of the channels 102 have cross-sectionaldimensions of at least 5 millimeters in width and at most 3 millimetersin depth. These dimensions can vary. In alternative embodiments, thesewidths and depths, and whether one or more channels should haveopenings, can be varied by a helmet designer.

In the example helmet shell 100 of FIGS. 1-6 , the multiple channels 102include two top channels 110 along a top or crown region of the helmetshell 100, a pair of left side channels 112 extending from a front leftedge of the helmet shell 100 toward the rear of the helmet shell 100along the left side of the helmet shell 100, a pair of right sidechannels 114 extending from a front right edge of the helmet shell 100toward the rear of the helmet shell 100 along the right side of thehelmet shell 100, a continuous rear channel 116 on the rear of thehelmet shell 100, and a pair of rear bottom channels 118 extending fromthe continuous rear channel 116 toward a bottom edge of the helmet shell100 at the rear of the helmet shell 100. Other embodiments of helmetshells may include a different arrangement of channels 102, additionalchannels 102, or fewer channels 102 in the outer surface than thosechannels 102 depicted in the example helmet shell 100 of FIGS. 1-6 .Also, in the example helmet shell 100 of FIGS. 1-6 , the pair of topslit openings 120 reside in the pair of top channels 110, the pair ofleft side slit openings 134 reside in the pair of left side channels112, the pair of right side slit openings reside in the pair of rightside channels 114, and the pair of rear slit openings 146 reside in thepair of rear bottom channels 118. The pairs of slit openings aredepicted as disposed within respective channels, however, the slitopenings may be disposed on shell body of the example helmet shell 100without some or all of the channels.

In the example helmet shell 100 of FIGS. 1-6 , the pair of top slitopenings 120 (and the two top channels 110) extend along the top of thehelmet shell 100, and are spaced apart from each other. The pair of topslit openings 120 and the two top channels 110 extend longitudinallyalong the top of the helmet shell 100, for example, from the front tothe back of the helmet shell 100. The top slit openings 120 and the twotop channels 110 are symmetrical with each other across a lateralcenterline of the helmet shell 100. The lateral centerline can include aplane that splits the left side of the helmet shell 100 from the rightside of the helmet shell 100. Some or all of the slit openings, channels102, or both, can be symmetrical across the lateral centerline of thehelmet shell 100. In some implementations, the entirety of the helmetshell 100 including the multiple channels 102 and slit openings issymmetrical across the lateral centerline of the helmet shell 100.

The pair of top slit openings 120 and the two top channels 110 arearranged to be substantially parallel to each other along the top of thehelmet shell 100, though the top channels 110 and/or top slit openings120 may not be exactly parallel to each other (at some or all pointsalong the length of the two channels or openings). For example, the pairof top slit openings 120 and the two top channels 110 of the examplehelmet shell 100 of FIGS. 1-6 run generally parallel to a longitudinalline from a front of the shell 100 to a back of the shell 100, but thechannels 110 and openings 120 can have a bow, or curve, along itsrespective longitudinal length, thereby creating a channel, opening, orboth, that is substantially, but not exactly, linear in the longitudinaldirection. For example, the top view of FIG. 6 shows the two topchannels 110 and the pair of top slit openings 120 of the example helmetshell 100 as having a laterally outward curve, or bow, along theirrespective lengths between the front and the back of the example helmetshell 100.

In some instances, such as depicted in the top view of FIG. 6 , each ofthe top channels 110 include the top slit opening 120, or vent, thatruns along a length of the top channels 110. In the example helmet shell100 of FIG. 6 , the slit opening 120 spans a majority of the length ofthe top channels 110, though the length of the top slit opening 120 canvary. The slit opening 120 can be a continuous opening along the lengthof the top channels 110, or a segmented opening with multiple uniform ornon-uniform openings within the top channels 110. Uniform openings canshare the same longitudinal length, the same lateral width, the sameshape, a combination of these, and/or other similarities.

The stiffness of the helmet shell 100 varies along the top channels 110and between the top channels 110 due, at least in part, to the top slitopenings 120. For example, the portion of the top channels 110 that donot include the slit openings 120 form areas of high stiffness 122, theportion of the top channels 110 that include the slit openings 120 formareas of low stiffness 124 (i.e., lower than the high stiffness), andthe portion of the helmet shell 100 between the top slit openings 120form a flex zone 126 configured to be more flexible than adjacentportions of the example helmet shell 100. The construction of the topchannels 110 and the slit openings 120 creates areas on the helmet shell100 that transition from high-to-low-to-high stiffness. In someinstances, the top slit openings 120 along the top channels 110 alsoprovide ventilation between an exterior and an interior of the helmetshell 100. The varying stiffness and flexibility of the helmet shell 100in the high stiffness areas 122, low stiffness areas 124, and flex zones126 create local flexibility (i.e., localized to the area represented bythe flex zone 126) that can be advantageous for absorbing, mitigating,and/or deflecting impact forces against the helmet shell 100.

In some implementations, each top slit opening of the pair of top slitopenings 120 has a first length, and the flex zone 126 defines aflexible helmet portion of the example helmet shell 100. The flexiblehelmet portion extends along the first length and between the pair oftop slit openings 120, and a stiffness of the flexible helmet portionvaries along the first length from a first longitudinal end of theflexible helmet portion (e.g., a front end) to a second longitudinal endof the flexible helmet portion (e.g., a rear end). For example, thestiffness of the flexible helmet portion includes a first stiffness atthe first end and at the second end of the flexible helmet portion, asecond stiffness at a middle portion of the flexible helmet portionbetween the first end and the second end, and a third stiffness at anintermediate portion of the flexible helmet portion between the firstend and the middle portion, and between the second end and the middleportion. The first stiffness is greater than the second stiffness, andthe third stiffness is greater than the second stiffness and less thanthe first stiffness. In other words, the stiffness of the flexiblehelmet portion varies from the first (highest) stiffness at the firstend, to the third (intermediate) stiffness adjacent to the first end, tothe second (lowest) stiffness at the middle of the flexible helmetportion, back to the third stiffness between the middle and the secondend, and further back to the first stiffness at the second end. Thesize, location, and shape of the top slit openings 120 can affect thefirst, second, and/or third stiffness at the flexible helmet portion.For example, a width and/or length of the slit opening may impact theflexibility and stiffness of the flexible helmet portion.

The pairs of slit openings, such as the pair of top slit openings 120,create flexible helmet portions at the portions of the shell bodybetween the pairs of slit openings. The flexibility and relativestiffnesses of these flexible portions can vary based on the length,size, and/or shape of the slit openings. In the present disclosure, slitopenings are identified in pairs to define a flexible helmet portionbetween the pairs of openings. However, flexible helmet portions canexist between slit openings on the example helmet shell 100 that are notidentified as pairs. For example, a flexible helmet portion may existbetween one of the top slit openings 120 and one of the left side slitopenings 134.

The top slit openings 120 have a rectangular shape along the topchannels 110. However, the shape of the slit openings 120 can vary. Forexample, the slit openings 120 can take on a non-uniform shape oranother appropriate shape, such as a shape that substantially or exactlymirrors the channel in which the opening is formed. The top slitopenings 120 can have a consistent/uniform width along its longitudinallength, and/or one or more of its longitudinal ends can have a taper,rounded end, angled end, or other shape. Alternatively, in someimplementations, the slit openings (including the top slit opening 120)can have widths that vary at different points along the longitudinallength of the opening. For example, the top slit openings 120 (and/orother slit openings of the present disclosure) can include tapered ends,such that the top slit openings 120 are widest at a middle of the slitopening 120, and gradually taper to a smaller width at ends of the slitopenings 120. Varying a width of the top slit openings 120 provides avarying flexibility (i.e., varying stiffness) in the adjacent flexibleportions of the example helmet shell 100.

The slit openings, such as the top slit openings 120 of the examplehelmet shell 100, can vary in size, shape, and location to provide adesired flexibility and stiffness to the adjacent flexible portions ofthe helmet shell 100. For example, the slit openings can be straight,can include one or more angles along its length, can include a curve(e.g., single curve, sinusoidal shape, or other curved shape), and/or acombination of these.

The flexible portions of the helmet shell 100 that reside between pairsof the slit openings provide flexibility that stems from the fact thattwo sides of the flexible portion are not directly connected to a sideof the helmet shell 100. Instead, the flexible portions are directlyconnected at two opposing sides and disconnected at the other twoopposing sides adjacent to the slit openings. This disconnect providesthe flexible portion of the helmet shell 100 a localized flexibility anda localized impact response. The slit openings are disposed along theexample helmet shell 100 to provide stiffer zones for certain types ofimpact (e.g., stiffer areas near the faceguard), and less stiff zonesfor other types of impact (e.g., on the sides for side helmet impact).

In some implementations, the flexible portions of the example helmetshell 100 (e.g., flex zone 126 and other flexible portions describedbelow) allows a designer to apply impact mitigating pads or otherstructures to the interior of the example helmet shell 100 that aredesigned for particular types of impact, thereby achieving a customimpact response throughout the helmet. In some instances, a largerdistance between pairs of slit openings provide for greater flex in theflexible portion between the pair of slit openings as compared to thepair of slit openings with a shorter distance between the slit openings.In certain instances, shorter pairs of slit openings create lessflexible and smaller flex portions of the helmet shell 100 compared tolonger pairs of slit openings, which would create more flexible andlarger flex portions of the helmet shell 100.

In some implementations, the portion of the example helmet shell 100that resides between the two top channels 110 includes a centralrecession 128 in the outer surface 104 of the helmet shell 100. Thecentral recession 128 resides between the two top channels 110, andextends along the lateral centerline of the helmet shell 100 between thetwo top channels 110. The central recession 128 includes a shallowdivot, concave recession, or other shaped recession in the outer surface104 of the helmet shell 100, where the central recession 128 is recessedinto the outer surface 104 of the helmet shell 100 such that it is morerecessed than adjacent portions of the outer surface 104 that residebetween the central recession 128 and the two top channels 110.

The example helmet shell 100 includes a front center plate 130 at afront center of the helmet shell 100. The front center plate 130 isintegrally formed with the helmet shell 100, and can be used as anattachment point for a face guard, face shield, face mask, or other faceprotection that covers at least part of the face opening of the examplehelmet shell 100. In the example helmet shell 100 of FIGS. 1-6 , thefront center plate 130 includes a trapezoidal shape, where an upperwidth of a top of the front center plate 130 is greater than a lowerwidth of a bottom of the front center plate 130. However, the shape ofthe front center plate 130 can vary. In some implementations, such as inthe example helmet shell 100 of FIGS. 1-6 , the multiple channels 102includes a continuous front channel 132 that partially surrounds thefront center plate 130. The continuous front channel 132 borders the topand sides of the front center plate 130, and can extends from a frontedge of the example helmet shell 100, around the front center plate 130,and back to the front edge. In some examples, the continuous frontchannel 132 excludes any through openings, for example, to providesufficient stiffness to the front center plate 130 in the event ofimpact forces against a face mask attached to the front center plate130. In the example helmet shell 100 of FIGS. 1-6 , the two top channels110 extend rearwardly from the continuous front channel 132, and in someexamples, can share the same dimensions as the continuous front channel132.

In certain implementations, the multiple channels 102 do not include thecontinuous front channel 132, in that the example helmet shell 100 doesnot include a channel surrounding the front center plate 130.

The pair of left side channels 112 extend from a front left edge of thehelmet shell 100 toward the rear of the helmet shell along a left sideof the helmet shell 100, and the pair of right side channels 114 extendfrom a front right edge of the helmet shell 100 toward a rear of thehelmet shell 100 along a right side of the helmet shell 100. The pair ofleft side channels 112 is symmetrical with the pair of right sidechannels 114 across the lateral centerline. The pair of left sidechannels 112 and right side channels 114 have portions that extendsubstantially linearly rearward from the respective front edges of theexample helmet shell 100, then turn at an angle (e.g., at transitionsection 113) toward a rear top of the example helmet shell 100, andfurther extend along a generally linear path. The shape of the pair ofleft side channels 112 and pair of right side channels 114 can vary fromthe angled shape of the example helmet shell 100 of FIGS. 1-6 .

The pair of left side channels 112 are depicted in the side view of theexample helmet shell 100 of FIG. 5 . In some instances, each of the leftside channels 112 include the side slit opening 134, or vent, that runsalong some or all of the lengths of the left side channels 112. In theexample helmet shell 100 of FIG. 5 , the left side slit openings 134span a majority of the length of the left side channels 112, though thelength of the side slit openings 134 can vary. The left side slitopening 134 can be a continuous opening along the length of the leftside channels 112, or a segmented opening with several uniform ornon-uniform openings within the left side channels 112. The pair of leftside slit openings 134 extend along the left side of the example helmetshell 100 toward the rear of the helmet shell 100, for example, alongthe pair of left side channels 112. However, the pair of left side slitopenings 134 may reside on the helmet shell 100 without the pair of leftside channels 112. The right side slit openings can be the same orsimilar to the left side slit openings 134 except mirrored on the rightside of the example helmet shell 100. The left side slit openings 134include portions that extend substantially linearly rearward from arespective front end of the slit opening, proximate to a front edge ofthe example helmet shell 100, then turn at an angle (e.g., at thetransition section 113) toward the rear top of the example helmet shell100, and further extend along a generally linear path. The shape of thepair of left slit openings 134 (and the mirrored pair of right slitopenings) can vary from the angled shape of the example helmet shell 100of FIGS. 1-6 .

The stiffness of the helmet shell 100 varies along the left sidechannels 112 and between the left side channels 112 due, at least inpart, to the side slit openings 134. For example, first portions 136 ofthe pair of left side channels 112 adjacent to longitudinal ends of theside slit openings 134 include a first, higher stiffness, secondportions 138 of the pair of left side channels 112 at the side slitopenings 134 include a second, lower stiffness (e.g., lower stiffnessthan the first, high stiffness), and an intermediate portion 140 of thehelmet shell 100 between the side slit openings 134 of the left sidechannels 112 form a flex zone configured to flex more than adjacentportions of the example helmet shell 100. The construction of the sidechannels 112 and the side slit openings 134 create areas on the side ofthe helmet shell 100 that transition from high-to-low-to-high stiffness.In some instances, the side slit openings 134 along the left sidechannels 112 also provide ventilation between an exterior and aninterior of the helmet shell 100. The varying stiffness and flexibilityof the helmet shell 100 in the high stiffness areas 136, low stiffnessareas 138, and flex zones 140 create local flexibility (represented bythe flex zone 140) that can be advantageous for absorbing, mitigating,and/or deflecting impact forces against the helmet shell 100.

In some implementations, each side slit opening of the pair of side slitopenings 134 has a second length, and the flex zone 140 defines anotherflexible helmet portion of the example helmet shell 100. The flexiblehelmet portion extends along the second length and between the pair ofside slit openings 134, and a stiffness of the flexible helmet portionvaries along the second length from a first longitudinal end of theflexible helmet portion (e.g., a front end) to a second longitudinal endof the flexible helmet portion (e.g., a rear end). For example, thestiffness of the flexible helmet portion includes a first stiffness atthe first end and at the second end of the flexible helmet portion, asecond stiffness at a middle portion of the flexible helmet portionbetween the first end and the second end, and a third stiffness at anintermediate portion of the flexible helmet portion between the firstend and the middle portion, and between the second end and the middleportion. The first stiffness is greater than the second stiffness, andthe third stiffness is greater than the second stiffness and less thanthe first stiffness. In other words, the stiffness of the flexiblehelmet portion varies from the first (highest) stiffness at the firstend, to the third (intermediate) stiffness adjacent to the first end, tothe second (lowest) stiffness at the middle of the flexible helmetportion, back to the third stiffness between the middle and the secondend, and further back to the first stiffness at the second end. Thesize, location, and shape of the side slit openings 134 can affect thefirst, second, and/or third stiffness at the flexible helmet portion.For example, a width and/or length of the slit opening may impact theflexibility and stiffness of the flexible helmet portion.

The side slit openings 134 of the example helmet shell 100 have arectangular shape along the left side channels 112 that taper in widthat a back end of the left side channels 112. However, the shape of theside slit openings 134 can vary. For example, the side slit openings 134can take on a non-uniform shape or another appropriate shape, such as ashape that substantially or exactly mirrors the channel that the openingis formed in. The side slit openings 134 can have a consistent widthalong its longitudinal length, and/or one or more of its longitudinalends can have a taper, rounded end, angled end, or other shape. Forexample, the left side slit openings 134 (and/or right side slitopenings) can include tapered ends, such that the left side slitopenings 134 are widest at a middle of the slit opening 134, andgradually taper to a smaller width at a rear end of the slit openings134. Varying a width of the side slit openings 134 provides a varyingflexibility (i.e., varying stiffness) in the adjacent flexible portionsof the example helmet shell 100.

The slit openings, such as the side slit openings 134 of the examplehelmet shell 100, can vary in size, shape, and location to provide adesired flexibility and stiffness to the adjacent flexible portions ofthe helmet shell 100. For example, the slit openings can be straight,can include one or more angles along its length, can include a curve(e.g., single curve, sinusoidal shape, or other curved shape), and/or acombination of these.

The right side channels 114 can include the same features as the leftside channels mirrored on the right side of the example helmet shell100. For example, the right side channels 114 can include right sideopenings to create areas of high stiffness, areas of low stiffness, anda flex zone on the right side of the helmet shell 100.

The continuous rear channel 116 at least partially surrounds a rearcenter zone 142 on the rear of the helmet shell 100. In the examplehelmet shell 100 of FIGS. 1-6 , the continuous rear channel 116completely surrounds the rear center zone 142. In other instances, thecontinuous rear channel 116 can partially surround the rear center zone142, such as only on the sides and/or top of the rear center zone 142.The pair of rear bottom channels 118 extend from the continuous rearchannel 116 toward a bottom edge of the helmet shell 100 at the rear ofthe helmet shell 100. The pair of rear bottom channels 118 can extendlaterally outward as the rear bottom channels 118 extend from thecontinuous rear channel 116 to the bottom edge of the helmet shell 100at the rear of the helmet shell 100. For example, the rear bottomchannels 118 border the sides of a rear zone 144 of the helmet shell100, where the rear zone 144 has an up tack shape.

In some implementations, the rear center zone 142 includes a trapezoidshape, and the continuous rear channel 116 surrounds the trapezoid shapeof the rear center zone 142.

The rear center zone 142, rear zone 144, continuous rear channel 116,and rear bottom channels 118 are depicted in the rear view of FIG. 3 .In the example helmet shell 100, the continuous rear channel 116excludes through openings between the inner surface 106 and the outersurface 104 of the helmet shell. However, the continuous rear channel116 may include slit openings, or vents. In some implementations, therear bottom channels 118 each include a rear slit opening 146, or vent,that runs along a portion of the length of the rear bottom channels 118.In the example helmet shell 100 of FIG. 3 , the rear slit openings 146span a portion of the length of the rear bottom channels 118, though thelength of the rear slit openings 146 can vary. The rear slit openings146 can be continuous openings along the portion of the length of therear bottom channels 118, or a segmented opening with multiple uniformor non-uniform openings within the rear bottom channels 118. Uniformopenings can share the same longitudinal length, the same lateral width,the same shape, a combination of these, and/or other similarities.

The stiffness of the helmet shell 100 varies along the rear bottomchannels 118 and within the rear zone 144 due, at least in part, to therear slit openings 146 within the rear bottom channels 118. For example,first portions 148 of the rear bottom channels 118 adjacent tolongitudinal ends of the rear slit openings 146 include a first, higherstiffness, second portions 150 of the pair of rear bottom channels 118at the rear slit openings 146 include a second, lower stiffness (e.g.,lower stiffness than the first, high stiffness), and an intermediateportion 152 of the rear zone 144 of the helmet shell 100 between therear slit openings 146 of the rear bottom channels 118 form a flex zoneconfigured to flex more than adjacent portions of the example helmetshell 100. The construction of the rear bottom channels 118 and the rearslit openings 146 create areas on the rear of the helmet shell 100 thattransition from high-to-low-to-high stiffness. In some instances, therear slit openings 146 along the rear bottom channels 118 also provideventilation between an exterior and an interior of the helmet shell 100.The varying stiffness and flexibility of the helmet shell 100 in thehigh stiffness areas 148, low stiffness areas 150, and flex zones 152create local flexibility (represented by the flex zone 152) that can beadvantageous for absorbing, mitigating, and/or deflecting impact forcesagainst the helmet shell 100.

In some implementations, each rear slit opening of the pair of rear slitopenings 146 has a third length, and the flex zone 152 defines aflexible helmet portion of the example helmet shell 100. The flexiblehelmet portion extends along the third length and between the pair ofrear slit openings 146, and a stiffness of the flexible helmet portionvaries along the third length from a first longitudinal end of theflexible helmet portion (e.g., a top end) to a second longitudinal endof the flexible helmet portion (e.g., a bottom end). For example, thestiffness of the flexible helmet portion includes a first stiffness atthe first end and at the second end of the flexible helmet portion, asecond stiffness at a middle portion of the flexible helmet portionbetween the first end and the second end, and a third stiffness at anintermediate portion of the flexible helmet portion between the firstend and the middle portion, and between the second end and the middleportion. The first stiffness is greater than the second stiffness, andthe third stiffness is greater than the second stiffness and less thanthe first stiffness. In other words, the stiffness of the flexiblehelmet portion varies from the first (highest) stiffness at the firstend, to the third (intermediate) stiffness adjacent to the first end, tothe second (lowest) stiffness at the middle of the flexible helmetportion, back to the third stiffness between the middle and the secondend, and further back to the first stiffness at the second end. Thesize, location, and shape of the top slit openings 120 can affect thefirst, second, and/or third stiffness at the flexible helmet portion.For example, a width and/or length of the slit opening may impact theflexibility and stiffness of the flexible helmet portion.

The rear slit openings 146 of the example helmet shell 100 have anirregular shape along an angled portion of the rear bottom channels 118.However, the shape of the rear slit openings 146 can vary. For example,the rear slit openings 146 can take on a uniform shape, non-uniformshape, or another appropriate shape, such as a shape that substantiallyor exactly mirrors the channel that the opening is formed in. The rearslit openings 146 can have a consistent width along its longitudinallength, and/or one or more of its longitudinal ends can have a taper,rounded end, angled end, or other shape.

Forming the slit openings in the example helmet shell 100 can providemultiple advantages, including providing areas of increased stiffness,such as in areas that are prone to higher volume of impacts (e.g., atthe side and rear zones of the example helmet shell 100). The slitopenings, and in some examples the slit openings and the channels,formed in the rear of the example helmet shell 100 can define higherstiffness zones, which is beneficial to mitigate the forces and energyof impacts to the rear of the example helmet shell 100.

The multiple channels 102 in the example helmet shell 100 form aninterconnected grid of channels in the outer surface 104 of the helmetshell 100. For example, the two top channels 110 extend into, orintersect, the continuous rear channel 116, and the pair of left sidechannels 112 and right side channels 114 intersect with the top channels110 at a rear top of the helmet shell 100. This interconnected gridconstruction allows the impact forces against the helmet shell 100 to bedispersed or dampened along the multiple channels 102. The multiplechannels 102 may include additional channels within the interconnectedgrid of channels. For example, an intermediate channel 154 extendsbetween the two top channels 110 and between the longitudinal end of thetopmost channel of the left side channels 112 and the longitudinal endof the topmost channel of the right side channel 114. The intermediatechannel 154 can be an extension of the left side channel and/or rightside channel that intersects one or both of the top channels 110 along atop rear of the example helmet shell 100. The intermediate channel 154is shown as aligned with the topmost channels of the left side channels112 and right side channels 114, though this can be misaligned in otherembodiments, such as further forward or further back from the positionshown in the example helmet shell 100 of FIGS. 1-6 . In certaininstances, a top portion of the continuous rear channel 116 extendsbetween the longitudinal end of the bottommost channel of the left sidechannels 112 and the longitudinal end of the bottommost channel of theright side channel 114. The intermediate channel 154 and the top portionof the continuous rear channel 116 can connect the pair of left sidechannels 112 with the pair of right side channels 114 to form acontinuous pair of channels that extend entirely around the examplehelmet shell 100.

In some instances, two adjacent slit openings (e.g., a top slit opening120 and an adjacent left side slit opening 134 or right side slitopening) can form another flex zone and additional areas of higherand/or lower stiffness of the example helmet shell 100. For example, theconstruction of the top slit opening 120 of the leftmost top channel 110and the side slit opening 134 of the topmost left side channel 112create areas on the side of the helmet shell 100 between the top channel110 and the left side channel 112 that transition fromhigh-to-low-to-high stiffness, and a flex zone between these respectiveopenings. The mirrored construction on the right side of the examplehelmet shell 100 can form a mirrored version of the samehigh-to-low-to-high stiffness and flex zone.

FIGS. 7 and 8 are a front view and a front perspective view,respectively, of a second example helmet shell 200 with slit openingsand multiple channels 202 disposed along the outer surface 104 of thehelmet shell 200. FIGS. 9, 10, 11, and 12 are a rear view, rearperspective view, side view, and top view, respectively, of the secondexample helmet shell 200 with the multiple slit openings. The secondexample helmet shell 200 is similar to the example helmet shell 100 ofFIGS. 1-6 , except that the second example helmet shell 200 does notinclude a continuous front channel 132, does not include the centralrecession 128, the left side channels 112′ and right side channels 114′are shaped to have a smaller angle (e.g., at transition section 213)along its length than the left side channels 112 and right side channels114 of the example helmet shell 100 of FIGS. 1-6 , and a rear of thesecond example helmet shell 200 includes a rear center zone 142′ and arear zone 144′ that is not separated by the continuous rear channel116′.

The outer surface of the helmet shell 100 along the rear center zone142′ and the rear zone 144′ are flush, in that the outer surface at therear center zone 142′ and the outer surface at the rear zone 144′ areflush with each other. The flex zone 152 of the second example helmetshell 200 may be the same size or a different size as the flex zone 152of the example helmet shell 100 of FIGS. 1-6 , for example, based on thesize and/or shape of the rear slit openings 146 along the pair of rearbottom channels 118.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyfeatures or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments. Certain features that aredescribed in this specification in the context of separate embodimentscan also be implemented in combination in a single embodiment.Conversely, various features that are described in the context of asingle embodiment can also be implemented in multiple embodimentsseparately or in any suitable subcombination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination may be directed to a subcombination or variation ofa subcombination.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

1. A helmet, comprising: a helmet shell comprising an outer surface, aninner surface, and a plurality of slit openings, wherein each slitopening extends along a portion of the helmet shell; the plurality ofslit openings comprising a pair of top slit openings that each extendlongitudinally along a top portion of the helmet shell, each top slitopening of the pair of top slit openings has a first length; the pair oftop slit opening being spaced apart and defining a flexible helmetportion spaced between the pair of top slit openings; and wherein theflexible helmet portion extends along the first length from a first endof the flexible helmet portion to a second end of the flexible helmetportion opposite to the first end, and the flexible helmet portion has astiffness that varies along the first length from the first end to thesecond end.
 2. The helmet of claim 1, wherein the stiffness of theflexible helmet portion comprises: a first stiffness at the first endand at the second end of the flexible helmet portion, a second stiffnessat a middle portion of the flexible helmet portion between the first endand the second end, and a third stiffness at an intermediate portion ofthe flexible helmet portion between the first end and the middleportion.
 3. The helmet of claim 2, wherein the first stiffness isgreater than the second stiffness, and the third stiffness is greaterthan the second stiffness and less than the first stiffness.
 4. Thehelmet of claim 1, wherein the helmet comprises a plurality channelsrecessed in the outer surface of the helmet shell, the plurality ofchannels comprising a pair of top channels along the top portion of thehelmet shell, and the pair of top slit openings reside within the pairof top channels.
 5. The helmet of claim 1, wherein the pair of top slitopenings are arranged substantially parallel to each other along the topportion of the helmet shell.
 6. The helmet of claim 1, wherein the pairof top slit openings are symmetrical with each other across a lateralcenterline of the helmet shell.
 7. The helmet of claim 1, wherein thepair of top slit openings are linear.
 8. The helmet of claim 1, whereineach of the top slit openings comprise a laterally outward curve.
 9. Thehelmet of claim 4, wherein the top slit opening of each top channel ofthe pair of top channels extends along a majority of a length of thepair of top channels.
 10. The helmet of claim 1, wherein the helmetshell comprises a central recession in the outer surface of the helmetshell in a crown region between the pair of top slit openings.
 11. Thehelmet of claim 1, wherein the plurality of slit openings furthercomprises: a pair of left side slit openings extending along a left sideof the helmet shell toward a rear of the helmet shell, and a pair ofright side slit openings extending along a right side of the helmetshell toward the rear of the helmet shell.
 12. The helmet of claim 11,wherein: each left side slit opening of the pair of left side slitopenings has a second length; the pair of left side slit opening arespaced apart and define a second flexible helmet portion spaced betweenthe pair of left side slit openings; and the second flexible helmetportion extends along the second length from a first end of the secondflexible helmet portion to a second end of the second flexible helmetportion opposite to the first end, and the second flexible helmetportion has a stiffness that varies along the second length from thefirst end to the second end of the second flexible helmet portion. 13.The helmet of claim 12, wherein the stiffness of the second flexiblehelmet portion comprises: a first stiffness at the first end and at thesecond end of the second flexible helmet portion, a second stiffness ata middle portion of the second flexible helmet portion between the firstend and the second end, and a third stiffness at an intermediate portionof the second flexible helmet portion between the first end and themiddle portion.
 14. The helmet of claim 13, wherein the first stiffnessis greater than the second stiffness, and the third stiffness is greaterthan the second stiffness and less than the first stiffness.
 15. Thehelmet of claim 11, wherein: the helmet comprises a plurality channelsrecessed in the outer surface of the helmet shell, the plurality ofchannels comprising a pair of left side channels along the left side ofthe helmet shell and a pair of right side channels along the right sideof the helmet shell, the pair of left side slit openings reside withinthe pair of left side channels, and the pair of right side slit openingsreside within the pair of right side channels.
 16. A helmet shell,comprising: a shell body; an outer surface of the shell body, an innersurface of the shell body, and a plurality of slit openings, whereineach slit opening extends along a portion of the helmet shell; and theplurality of slit openings comprising: a pair of left side slit openingsextending along a left side of the shell body toward a rear of the shellbody, each left side slit opening of the pair of left side slit openingscomprising a first length, and a pair of right side slit openingsextending along a right side of the shell body toward a rear of theshell body, each right side slit opening of the pair of right side slitopenings comprising a second length; wherein the pair of left side slitopenings being spaced apart and defining a left flexible helmet portionbetween the pair of left side slit openings, the left flexible helmetportion extending along the first length from a first end of the leftflexible helmet portion to a second end of the left flexible helmetportion opposite to the first end, and the left flexible helmet portioncomprising a stiffness that varies along the first length from the firstend to the second end; and wherein the pair of right side slit openingsbeing spaced apart and defining a right flexible helmet portion betweenthe pair of right side slit openings, the right flexible helmet portionextending along the second length from a third end of the right flexiblehelmet portion to a fourth end of the right flexible helmet portionopposite to the third end, and the right flexible helmet portioncomprising a stiffness that varies along the second length from thethird end to the fourth end.
 17. The helmet shell of claim 16, whereinthe stiffness of the left flexible helmet portion comprises: a firststiffness at the first end and at the second end of the left flexiblehelmet portion, a second stiffness at a middle portion of the leftflexible helmet portion between the first end and the second end, and athird stiffness at an intermediate portion of the left flexible helmetportion between the first end and the middle portion.
 18. The helmetshell of claim 17, wherein the stiffness of the right flexible helmetportion comprises: the first stiffness at the third end and at thefourth end of the right flexible helmet portion, the second stiffness ata second middle portion of the right flexible helmet portion between thethird end and the fourth end, and the third stiffness at a secondintermediate portion of the right flexible helmet portion between thethird end and the second middle portion.
 19. The helmet shell of claim17, wherein the first stiffness is greater than the second stiffness,and the third stiffness is greater than the second stiffness and lessthan the first stiffness.
 20. The helmet shell of claim 16, wherein: thehelmet shell comprises a plurality channels recessed in the outersurface of the helmet shell, the plurality of channels comprising a pairof left side channels along the left side of the helmet shell and a pairof right side channels along the right side of the helmet shell, thepair of left side slit openings reside within the pair of left sidechannels, and the pair of right side slit openings reside within thepair of right side channels.
 21. The helmet shell of claim 16, whereinthe pair of left side slit openings and the pair of right side slitopenings are linear.
 22. A helmet shell, comprising: a shell body; anouter surface and an inner surface of the shell body, and a plurality ofslit openings extending along a portion of the helmet shell; and theplurality of slit openings comprising a pair of rear slit openings at arear of the helmet shell, the pair of rear slit openings partiallysurrounding a rear zone at the rear of the helmet shell and comprising afirst length.
 23. The helmet shell of claim 22, wherein: the pair ofrear slit openings are spaced apart and define a rear flexible helmetportion between the pair of rear slit openings, the rear flexible helmetportion extending along the first length from a first end of the rearflexible helmet portion to a second end of the rear flexible helmetportion opposite to the first end, the rear flexible helmet portioncomprising a stiffness that varies along the first length from the firstend to the second end.
 24. The helmet shell of claim 23, wherein thestiffness of the rear flexible helmet portion comprises: a firststiffness at the first end and at the second end of the rear flexiblehelmet portion, a second stiffness at a middle portion of the rearflexible helmet portion between the first end and the second end, and athird stiffness at an intermediate portion of the rear flexible helmetportion between the first end and the middle portion.
 25. The helmetshell of claim 24, wherein the first stiffness is greater than thesecond stiffness, and the third stiffness is greater than the secondstiffness and less than the first stiffness.
 26. The helmet shell ofclaim 22, wherein the pair of rear slit openings are straight.
 27. Thehelmet shell of claim 22, wherein the pair of rear slit openings aresymmetrical across a lateral centerline of the helmet shell.